In the prior art, there has been known a temperature sensor, as called the “exhaust temperature sensor”, which is disposed in the exhaust pipe of the vehicle and used for detecting the temperature of the exhaust gas. Moreover, a known temperature sensor of this kind has a structure, in which a ceramic substrate having a metallic resist or made of a material of a platinum-group is mounted as a temperature sensing portion (as referred to JP-A-2002-168701).
A detailed construction of the temperature sensor is shown in FIG. 7. A ceramic substrate 81 is fixed by a holding member 90 in a cylindrical case 80 made of a metal. The ceramic substrate 81 is formed into a slender plate shape having wiring layers 81a applied on its one face, as shown in FIG. 8. A metallic resistor 82 made of a thermistor material of a platinum group or the like is printed on the leading end side of the ceramic substrate 81. On the trailing end side of the ceramic substrate 81, there are fixed terminals 83, which are electrically connected with the metallic resistor 82 through the wiring layers 81a. The terminals 83 of the ceramic substrate 81 are connected with the cores 92 of an Mineral Insulated (“MI”) cable 91 extending through a spacer 93 from the case 80, as shown in FIG. 7. At a position of a length L1 from the leading end of the case 80, on the other hand, there is formed a flange portion 80a, around which a nut 94 is turnably mounted. On the leading end side of this flange portion 80a, there is formed a seal surface 80c, which makes close contact with the mounting seat face of the exhaust pipe thereby to prevent the exhaust gas from leaking out. In the leading end side of the case 80, moreover, there are formed a plurality of fluid communication ports 80b for providing the communication of the exhaust gas with the inside of the case 80. Here, the MI cable 91 is called the “sheath core”, too, and is provided with the cores 92 inside of a cylindrical outer cylinder made of a metal. This outer cylinder is insulated and filled with ceramics or the like so that the cores 92 are held while being insulated from the outer cylinder.
In this temperature sensor, the metallic resistor 82 outputs a resistance varying with the temperature of the exhaust gas, as an electric signal, which is extracted to the outside of the case 80 by the cores 92 of the MI cable 91. Thus, the temperature of the exhaust gas is measured by the temperature sensor so that the engine or the like of the vehicle is properly controlled according to the measured temperature.